#include <string>
#include <ros/ros.h>
#include <sensor_msgs/JointState.h>
#include <tf/transform_broadcaster.h>
#include <nav_msgs/Odometry.h>

int main(int argc, char** argv)
{
  ros::init(argc, argv, "state_publisher");
  ros::NodeHandle n;
  ros::Publisher odom_pub = n.advertise<nav_msgs::Odometry>("odom",10);

  //initial position
  double x = 0.0;
  double y = -3.0;
  double th = 0;

  //velocity
  double vx = 1.0;
  double vy = 0.0;
  double vth = 0.4;
  ros::Time current_time;
  ros::Time last_time;
  current_time = ros::Time::now();
  last_time = ros::Time::now();

  tf::TransformBroadcaster broadcaster;
  ros::Rate loop_rate(20);

  const double degree = M_PI/180;

  //message declarations
  geometry_msgs::TransformStamped odom_trans;
  odom_trans.header.frame_id = "odom";
  odom_trans.child_frame_id = "base_footprint";

  while (ros::ok()) {
    current_time = ros::Time::now();

    double dt = (current_time - last_time).toSec();
    double delta_x = (vx * cos(th) - vy * sin(th)) * dt;
    double delta_y = (vx * sin(th) + vy * cos(th)) * dt;
    double delta_th = vth*dt;

    x += delta_x;
    y += delta_y;
    th += delta_th;

    geometry_msgs::Quaternion odom_quat;
    odom_quat = tf::createQuaternionMsgFromRollPitchYaw(0,0,th);

    //updata transform
    odom_trans.header.stamp = current_time;
    odom_trans.transform.translation.x = x;
    odom_trans.transform.translation.y = y;
    odom_trans.transform.translation.z = 0;
    odom_trans.transform.rotation = tf::createQuaternionMsgFromYaw(th);

    //filling the odometry
    nav_msgs::Odometry odom;
    odom.header.stamp = current_time;
    odom.header.frame_id = "odom";
    odom.child_frame_id = "base_footprint";
    //position
    odom.pose.pose.position.x = x;
    odom.pose.pose.position.y = y;
    odom.pose.pose.position.z = 0.0;
    odom.pose.pose.orientation = odom_quat;

    //velocity
    odom.twist.twist.linear.x = vx;
    odom.twist.twist.linear.y = vy;
    odom.twist.twist.linear.z = 0;
    odom.twist.twist.angular.x = 0;
    odom.twist.twist.angular.y = 0;
    odom.twist.twist.angular.z = vth;

    last_time = current_time;

    //plublishing the odometry and new tf
    broadcaster.sendTransform(odom_trans);
    odom_pub.publish(odom);

    loop_rate.sleep();
  }
  return 0;
}
